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authorEric W. Biederman <ebiederm@xmission.com>2014-05-30 11:04:00 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-06-26 15:15:38 -0400
commit17f46a4cedce238dc24a21674756a732816d6f0c (patch)
tree2d795fdb1482f8dbdf88392ee51b609eca48bad4 /net
parentbe0ef855baab7248d0fc71cdf78a47fcfd3708f1 (diff)
netlink: Only check file credentials for implicit destinations
[ Upstream commit 2d7a85f4b06e9c27ff629f07a524c48074f07f81 ] It was possible to get a setuid root or setcap executable to write to it's stdout or stderr (which has been set made a netlink socket) and inadvertently reconfigure the networking stack. To prevent this we check that both the creator of the socket and the currentl applications has permission to reconfigure the network stack. Unfortunately this breaks Zebra which always uses sendto/sendmsg and creates it's socket without any privileges. To keep Zebra working don't bother checking if the creator of the socket has privilege when a destination address is specified. Instead rely exclusively on the privileges of the sender of the socket. Note from Andy: This is exactly Eric's code except for some comment clarifications and formatting fixes. Neither I nor, I think, anyone else is thrilled with this approach, but I'm hesitant to wait on a better fix since 3.15 is almost here. Note to stable maintainers: This is a mess. An earlier series of patches in 3.15 fix a rather serious security issue (CVE-2014-0181), but they did so in a way that breaks Zebra. The offending series includes: commit aa4cf9452f469f16cea8c96283b641b4576d4a7b Author: Eric W. Biederman <ebiederm@xmission.com> Date: Wed Apr 23 14:28:03 2014 -0700 net: Add variants of capable for use on netlink messages If a given kernel version is missing that series of fixes, it's probably worth backporting it and this patch. if that series is present, then this fix is critical if you care about Zebra. Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r--net/netlink/af_netlink.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 6d69c27897f3..7f40fd25acae 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1373,7 +1373,9 @@ retry:
bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
struct user_namespace *user_ns, int cap)
{
- return sk_ns_capable(nsp->sk, user_ns, cap);
+ return ((nsp->flags & NETLINK_SKB_DST) ||
+ file_ns_capable(nsp->sk->sk_socket->file, user_ns, cap)) &&
+ ns_capable(user_ns, cap);
}
EXPORT_SYMBOL(__netlink_ns_capable);
@@ -2293,6 +2295,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
struct sk_buff *skb;
int err;
struct scm_cookie scm;
+ u32 netlink_skb_flags = 0;
if (msg->msg_flags&MSG_OOB)
return -EOPNOTSUPP;
@@ -2314,6 +2317,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
if ((dst_group || dst_portid) &&
!netlink_allowed(sock, NL_CFG_F_NONROOT_SEND))
goto out;
+ netlink_skb_flags |= NETLINK_SKB_DST;
} else {
dst_portid = nlk->dst_portid;
dst_group = nlk->dst_group;
@@ -2343,6 +2347,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
NETLINK_CB(skb).portid = nlk->portid;
NETLINK_CB(skb).dst_group = dst_group;
NETLINK_CB(skb).creds = siocb->scm->creds;
+ NETLINK_CB(skb).flags = netlink_skb_flags;
err = -EFAULT;
if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {